A switch mode power supply (SMPS) is an electronic power supply unit (PSU) that incorporates a switching regulator. In particular, a SMPS may include a buck-boost voltage regulator capable of converting from input voltages above, below, or equal to the controlled output voltage, respectively performing buck mode regulation, boost mode regulation, or buck-boost mode regulation. Buck-boost regulator architecture typically is provided for power supplies used for automotive applications, lap-top computers, telecom equipment and distributed power systems. For example, the LTC3440 buck-boost converter manufactured by Linear Technology Corporation, assignee of the present application, includes four switches, two of which are connected to the input side of an inductor, and the other two are connected to the output side. In accordance with the level of voltage output to be controlled and the level of voltage input, the regulator has the capability of assuming a plurality of operation states in which the switches are sequentially activated or deactivated, to connect the inductor to the input, the output, and/or a common ground connection.
Another example is the LTC3780 four-switch buck-boost switching regulator manufactured by Linear Technology Corporation. This is a current mode regulator that provides an output voltage above, below or equal to the input voltage. The operating mode of the controller is determined through the voltage applied to the Forced Continued Control Input pin. The power switches are controlled so as to provide continuous transfers between modes of operation.
However, implementation of known buck-boost switching regulators requires a complex circuit arrangement. Also, typical buck-boost regulator architecture does not allow peak current mode control and Burst Mode® operation.
Hence, there is a need for simpler circuitry and methodology for enabling a voltage regulator to switch between buck and boost modes while allowing peak current mode control and Burst Mode operation.